Watermarking of digital content is an effective means for identifying copyright information. A digital watermark is data that is encoded into digital content in a manner that may or may not be humanly perceptible. In general, watermarks may be encoded into the digital content in either the spatial domain or the frequency domain. Watermarks provide a way to add non-removable or editable information to content with no or minimal degradation to the original content. Depending on the specific watermark technology, it may be difficult or even impossible to remove the watermark without severely degrading content quality. Companies such as Digimark and Verimatrix have implemented successful digital watermarking technologies for still photos and video imaging respectively.
In a broadcast or multicast video transport system, digital watermarking can most easily be accomplished at the source of the video broadcast. This approach delivers video content having a common watermark to each termination or client receiving the broadcast and can clearly provide a non-removable label identifying copyright restrictions. However, this common watermark provides no deterrent to the user against anonymous redistribution. Such redistribution can occur through public Peer-to-Peer (P2P) networks, darknets, or postings to video sharing sites. As such, it is desirable to use client-side watermarking at the termination of the multicast to clearly identify the end user. If the user then redistributes the content illegally, the watermark may be used to trace the content to the user.
In order to apply a high fidelity, robust watermark, it is desirable to apply the watermark to non-compressed content or content that has been transmitted in a lossless format. Thus, for client-side watermarking in a video distribution system, an issue arises due to the fact that the distributed video content is highly compressed. Traditionally, the client decompresses the compressed video content, applies the watermark, and then re-compresses the watermarked video content. However, as a result of the decompression, watermarking, and re-compression of the watermarked content, the quality of the video content may be significantly reduced. Recent advances in technology enabling increased compression ratios further compound this issue. For example, the H.264 (or MPEG4 Part 10) standard has a compression ratio of 1:32 which is twice that of an MPEG2. The increased compression ratio of H.264 makes effective client-side watermarking increasingly more difficult due to the lossy nature of the compression.
Thus, there is a need for a system and method for providing client-side watermarking in a manner that does not significantly reduce the quality of the digital content.